docs: def _list_subnets_by_identifier(self, identifier):
          """Returns a list of IDs of the subnet matching the identifier.
  
          :param string identifier: The identifier to look up
          :returns: List of matching IDs
          """
          identifier = identifier.split('/', 1)[0]
  
          results = self.list_subnets(identifier=identifier, mask='id')
          return [result['id'] for result in results]